1. Field of the Invention
The present invention relates generally to a reciprocating compressor, and more particularly it relates to a reciprocating compressor using a chlorine-free fluorocarbon refrigerant having a critical temperature of above 40.degree. C. and ester oils as a refrigerating machine oil, which contains a mixture of wax and ester oil as a winding oil for enamel wire of the motor insulating layer of the compressor.
2. Description of the Related Arts
In recent years, chlorine-containing chlorofluorocarbons have been included in the list of the compounds under regulation in use all over the world because of the problems involving environmental pollution, in particular, ozone depletion and global warming. All of flons included in the list of compounds under regulation in use are chlorine-containing chlorofluorocarbons such as R11, R12, R113, R114, R115, etc. In particular, R12 has been exclusively used as a refrigerant in refrigerating apparatus such as refrigerators, dehumidifiers, etc.
Accordingly, a refrigerant, which contains no chlorine in the molecule and is usable in place of R12, is required. Hydrofluorocarbon (HFC) or fluorocarbon have been noted as a substitute refrigerant. The examples of chlorine-free hydrofluorocarbon or fluorocarbon are listed below. Among others, R134a (1,1,1,2-tetrafluoroethane, CH.sub.2 FCF.sub.3) is a typical example of such a refrigerant and chiefly studied. The chlorine-free hydrofluorocarbon or fluorocarbon has an unique chemical structure and hence very characteristic properties. Therefore, it has a very poor compatibility with refrigerating machine oils such as mineral oils and alkylbenzene oils which have been used in the conventional refrigeration system using R12 refrigerant, and hence it cannot be put into practical use at all. Thus, R134a adversely affects the lubrication and the resistance to frictional wear of the sliding portions of compression mechanical parts, and electrical insulating materials.
To avoid the problems associated with the incompatibility of R134a with refrigerating machine oil, it has been proposed to use ester oils of one or more fatty acids, which contains at least two ester linkages in the molecule (EP 485 979B1).
The conventional refrigerant compressor is shown in FIG. 1 and FIG. 2. FIG. 10A and FIG. 10B are systemic and schematic diagrams of refrigerating cycle for refrigeration apparatus, respectively. With reference to FIG. 10A and FIG. 10B, the refrigerating cycle comprises a compressor section 1, an expansion mechanism 7, a condenser 2,3,4,5, and an evaporator 8. Further, as shown in FIG. 1 and FIG. 2, the compressor comprises a closed vessel stored with refrigerating oil which accommodates a motor 101, a cover suction muffler 102, a suction spring 103, a suction pipe 104, a discharging pipe 105 and an assembly suction muffler 106. The electric motor of the compressor is composed of a stator and a rotor, which contains an insulating film 20 or 30. A rotating shaft as fitted in the rotor and the compressor section connected to the motor through the rotating shaft.
The structure of the electrically insulating enamel wire is depicted in FIG. 3 and FIG. 4. FIG. 3 and FIG. 4 depict the conventional insulating film and the inventive insulating film, respectively. They have the same structure, except the kind of winding oil (34 in FIG. 3, and 24 in FIG. 4). With reference to FIG. 3 and FIG. 4, a copper core wire 31 or 21 is double-coated with a polyester imide film 32 or 22 and then polyamide-imide film 33 or 23. Paraffin wax 34 or 24 as a winding oil is coated on the polyamide-imide film. An enamel wire is composed of a conductor 31 or 21, an insulating material 32 and 33, or 22 and 23, and a winding oil 34 or 24. The conductor is made of pure (above 99.9%) copper, and the polyester imide and polyamide-imide films are used as an insulating material. A winding oil such as paraffin wax is coated on the insulating material to improve the workability of the motor during its manufacturing.
An enamel wire is employed as a winding wire of electric and electronic appliances to interconvert the electric energy to the mechanical energy, vice versa.
For the conventional compressor containing R-12 and a mineral oil-based refrigerating machine oil, when paraffin wax is used as winding oil for motor insulating enamel wire, the paraffin wax shows good compatibility with the mineral oil used as a refrigerating machine oil.
However, for the compressor containing R-134a and an ester oil-based refrigerating machine oil, if paraffin wax is used as a winding oil for the motor insulating enamel wire, the paraffin wax, which is non-polar, shows a very poor miscibility with the ester oil, which is polar, resulting in a blockage of a capillary, in particular of the opening of the capillary which has a relatively low temperature and consequently a deterioration of the performance of the refrigerating apparatus.
Accordingly, there has been a need to provide a new winding oil which can be advantageously used for the insulating layer of the compressor containing R-134a and ester oil-based refrigerating machine oil and shows good compatibility or miscibility with R-134a and refrigerating machine oil.